A numeric digit used to ensure that account numbers are entered accurately into the computer. Check digits are computed when the numbers are generated, and they become part of the number, often at the ...

Barcode technology makes real-time data collection possible. Despite the multitude of barcodes in existence today, universal product codes remain among the most useful to a small business. Because UPC ...

You’re at the checkout screen after an online shopping spree, ready to enter your credit card number. You type it in and instantly see a red error message ...

Katie has a PhD in maths, specializing in the intersection of dynamical systems and number theory. She reports on topics from maths and history to society and animals. Katie has a PhD in maths, ...